The present invention relates to the mechanical and optical connection of optical fibers within an optical system, and more particularly, to a hermetically sealed fiber tail assembly for connecting optical fibers to an optical device
Optical fiber networks provide high-capacity communications with increased reliability at greatly reduced costs. Such networks often include components that are both sensitive to environmental conditions and installed in harsh environments. Further improvement in the reliability and cost of communications requires protection of optical components from such environments.
In an optical network, optical fibers are typically connected to optical components such as signal transmitters, modulators, signal testers, switches, fiber splices, signal splitters, amplifiers, or receivers. A fiber tail assembly (“FTA”) may be placed on the optical fiber and the optical component to facilitate mechanical and optical coupling between the two. Optical components may be hermetically sealed in a device housing to prevent the device's being damaged by seepage of external elements into the package. However, in order to maintain a hermetic seal and protection of an optical component, the FTA must also be hermetically sealed to the fiber and to the component.
A component may be hermetically sealed to an optical fiber by metalizing the fiber and soldering a component to the metalized fiber surface. However, fiber metalization can reduce the strength of the glass fiber by introducing high surface stress, usually from slippage and/or metal spiking in the first adhesion layer that contacts the glass surface. Therefore, metalized fibers can be weak and break during assembly or, worse yet, while operating in the field.
Fiber metalization can also induce stress in the fiber that is not symmetric about the fiber axis. Such asymmetric stress can produce an asymmetric change in the fiber's refractive index that degrades the performance of polarization maintaining fiber (“PMF”) by reducing its ability to maintain the polarization state of light that it carries. Furthermore, if melting temperatures of the metalization layer and the hermetic seal of the FTA are not sufficiently high, then the fiber metalization or the hermetic seal may be destroyed when the FTA is sealed to an optical component.
Thus, there is a need for an FTA that can be hermetically sealed to an optical fiber and to an optical component reliably and without damaging the mechanical or optical properties of the fiber.